﻿select * from t1 CROSS JOIN t2;
select * from t1 INNER JOIN t2 on t1.num=t2.num;
select * from t1 INNER JOIN t2 using (num);
select * from t1 NATURAL INNER JOIN t2 ;
select * from t1 LEFT JOIN  t2 on t1.num=t2.num;
select * from t1 RIGHT JOIN  t2 on t1.num=t2.num;
select * from t1 FULL JOIN  t2 using (num);
select * from t1 RIGHT JOIN t2 on t1.num=t2.num;
select * from t1 LEFT JOIN t2 on t1.num=t2.num AND t2.value='xxx';
select * from t1 LEFT JOIN t2 on t1.num=t2.num WHERE t2.value='xxx';
